 
    //获取ul
    let ul_list = document.getElementById('ulList');
    //获取a标签
    let aList = document.querySelectorAll('a');
    // alert(aList.length)
    
    setInterval(()=>{
        let leftValue = ul_list.offsetLeft;
        // alert(leftValue) //
        if(leftValue < -1650){
            leftValue = 550;
        }
        ul_list.style.left = leftValue - 550 +'px';
    },2000)

    var index =0;
    aList[index].style.backgroundColor = 'black';
    

    for(let i = 0;i < aList.length;i++){ 
        aList[i].onclick = function(){
            let change = -550*i; 
            // alert(change)
            ul_list.style.left = change + 'px'; 
            // console.log('1111');
            
        }
    };


 